News Release

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Jun. 21, 2017--
Ra
Pharmaceuticals, Inc. (NASDAQ:RARX) today announced that it will
host a conference call and webcast on Tuesday, June 27, 2017 to discuss
initial data from the Company’s global Phase 2 clinical program
evaluating RA101495 for the treatment of paroxysmal nocturnal
hemoglobinuria (PNH). Early safety, tolerability, preliminary efficacy
and pharmacodynamic data on the first two treatment naïve patients
enrolled will be presented.

Ra Pharma is a clinical stage biopharmaceutical company focusing on the
development of next-generation therapeutics for the treatment of
complement-mediated diseases and is developing RA101495 as a novel,
subcutaneously-administered (SC) inhibitor of complement component 5
(C5).

Details of the conference call and webcast are as follows:

Date:

Tuesday, June 27, 2017

Time:

8:00 a.m. ET

Telephone Access:

Domestic callers, dial 844-419-1655,

International callers, dial 216-562-0467,

Reference the Ra Pharmaceuticals conference call;

Online Access:

Go to the Investor Relations section of the Ra Pharma website (http://ir.rapharma.com/phoenix.zhtml?c=254447&p=irol-calendar)
and follow instructions for accessing the live webcast. Please
connect to the website at least 15 minutes prior to the start of
the conference call to ensure adequate time for any software
download that may be necessary.

Ra Pharma is developing RA101495 for paroxysmal
nocturnal hemoglobinuria (PNH), refractory
generalized myasthenia gravis (rMG), and lupus
nephritis (LN). The product is designed for convenient, once daily
SC self-administration. RA101495 is a synthetic, macrocyclic peptide
discovered using Ra Pharma’s powerful proprietary drug discovery
technology. The peptide binds complement component 5 (C5) with
sub-nanomolar affinity and allosterically inhibits its cleavage into C5a
and C5b upon activation of the classical, alternative or lectin
pathways. By binding to a region of C5 corresponding to C5b, RA101495
also disrupts the interaction between C5b and C6 and prevents assembly
of the membrane attack complex (MAC). This activity defines an
additional, novel mechanism for the inhibition of C5 function. In Phase
1 studies, dosing of RA101495 was well tolerated in healthy volunteers
and demonstrated sustained and near complete suppression of hemolysis
and complement activity. To learn more about RA101495, please visit: http://rapharma.com/pipeline/ra101495/.

About RA101495 Phase 2 Clinical Program

The global, dose-finding Phase 2 program is designed to evaluate the
safety, tolerability, preliminary efficacy, pharmacokinetics, and
pharmacodynamics of RA101495 in patients with PNH. The study will
evaluate RA101495 in three cohorts. Cohort A includes eculizumab-naïve
patients, Cohort B includes patients switching from eculizumab to
RA101495, and Cohort C includes patients who are currently treated with
eculizumab but have evidence of an inadequate response. Patients in all
three cohorts will be eligible for a long-term extension study following
the completion of the initial 12-week studies. The primary efficacy
endpoint is change in lactate dehydrogenase from baseline to the mean
level from Week 6 to week 12.

About Ra Pharmaceuticals

Ra Pharmaceuticals is a clinical stage biopharmaceutical company
focusing on the development of next-generation therapeutics for
complement-mediated diseases. The Company discovers and develops
peptides and small molecules to target key components of the complement
cascade. For more information, please visit: www.rapharma.com.

Forward-Looking Statement

This press release contains "forward-looking statements" within the
meaning of the Private Securities Litigation Reform Act of 1995,
including, but not limited to, statements regarding the safety, efficacy
and regulatory and clinical progress of our product candidates,
including RA101495. All such forward-looking statements are based on
management's current expectations of future events and are subject to a
number of risks and uncertainties that could cause actual results to
differ materially and adversely from those set forth in or implied by
such forward-looking statements. These risks and uncertainties include
the risks that Ra Pharma’s product candidates, including RA101495, will
not successfully be developed or commercialized; the risk that initial
data from the Company’s global Phase 2 clinical program evaluating
RA101495 for the treatment of PNH may not be indicative of final study
results; the risk that initial data from a limited number of patients
may not be indicative of results from the fully patient enrollment
planned for such study; as well as the other factors discussed in the
“Risk Factors” section in Ra Pharma’s most recently filed Annual Report
on Form 10-K, as well as other risks detailed in Ra Pharma’s subsequent
filings with the Securities and Exchange Commission. There can be no
assurance that the actual results or developments anticipated by Ra
Pharma will be realized or, even if substantially realized, that they
will have the expected consequences to, or effects on, Ra Pharma. All
information in this press release is as of the date of the release, and
Ra Pharma undertakes no duty to update this information unless required
by law.